Minimum Replacements to Make String Symmetric

You are given a string \(s\) consisting of lowercase English letters. Your task is to compute the minimum number of character replacements required so that the string becomes symmetric (i.e. a palindrome).

A string is symmetric if for all \(0 \le i < n/2\), the following holds:

[ s[i] = s[n-i-1] ]

For example, for the string "abca", replacing the character at index 1 or index 2 will yield a symmetric string, hence the answer is 1.

Input: A single string \(s\) read from standard input.

Output: An integer denoting the minimum number of replacements needed.

inputFormat

The input is a single line containing the string (s) consisting only of lowercase English letters. The string may be of any length from 1 to (10^5).

outputFormat

Output a single integer which is the minimum number of replacements needed to make the string symmetric.## sample

abca

1